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Old 18th April 2010, 01:20 AM   #601
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Here it is, the new Mark 4 Crossover:

Click the image to open in full size.

The three added 33R resistors are R5, R6 and R7 - they are listed as Optional Shunt Damping - so whether you take up that option or not, that is what distinguishes if you have Mark 3 and Mark 4.

Details will be posted here soon and on the website - the reasons why and also the option to vary (tweak) the 33R value. IF you change this value they should all three (per crossover, so a total of six) be the same. They should not be less than 33R - experimenting with values up to 100R max (above that value they will have too small an effect). Experimentation should prove quite easy to do.

I am using 33R in my Elsinores right now and very pleased with the result. So that will likely stay the official value.

The improvement largely depends on the amplifier you use. It may well have a larger improvement with valve/tube amps, especially single end and JLTi Unity Coupling Amplidiers EL34 and KT88 - where the improvement is quite dramatic.

But as the Mark 4 revision makes the load on the amplifier a lot less resistive, espcially in the 70-90 Hertz region, many solid state amplifers (not all of them like reactive loads) may also show significant improvement.

All this will come out in the wash as we get feedback.

Cheers, Joe

PS: Sometimes it's good to wear two hats. It has helped that I do both amplifier design and speaker design. Not trying to be immodest, but most speaker designers do only speakers and it is important to see things from the amplifier side too. The Mark 4 upgrade is really about the amplifier and seeing that its needs are also met.
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Old 18th April 2010, 05:00 PM   #602
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Greetings Joe, just to let you know i have choosen to undertake the Elsinore build. This will be my first DIY project and am really looking forward to it.
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Old 18th April 2010, 08:10 PM   #603
rob323 is offline rob323  Australia
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Joe,
Would this help reduce the bass bloom experienced when we plugged a tube amp into my Elsinores recently (which I assume was just because of lack of dampening)?
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Old 29th April 2010, 02:14 PM   #604
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Default another change needed?

In the PDFs of Scan-Speakís D2608 Discovery tweeter and the Peerless HDS 810921, there are differences.

While the 810921ís PDF was stamped Preliminary, and has a lot less specs, the Sensitivity may not be as high - though the 810921 didnít say if it was @ 2.83 V/ 1m.

More importantly, the response at 30 and 60 degrees apparently now drops off faster . .
Attached Files
File Type: pdf Peerless 810921 - Elsinore driver.pdf (187.9 KB, 41 views)
File Type: pdf Scan-Speak d2608 - 913000.pdf (131.6 KB, 37 views)
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Old 30th April 2010, 06:12 AM   #605
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Quote:
Originally Posted by rob323 View Post
Joe,
Would this help reduce the bass bloom experienced when we plugged a tube amp into my Elsinores recently (which I assume was just because of lack of dampening)?
YES! To the first part.

The second part re damping is more complex.

Indeed that (first part) was what motivated the change. But it turned out to do somewhat more than that.

The difference with solid state amp is yet to be verified.

No it was not damping perse'. It is more to do with lessening the reactive Q associated with the Z plot and reacting to that.

Here are some graphs that shows the differences caused by now going to Mark 4.

The first shows only a minore change to the frequency response. Red is old Mark 3 and Blue is Mark 4:

Click the image to open in full size.

Not a great change in frequency response.

Let us look at the difference in the Z plot, the impedance curver:

Click the image to open in full size.

The overall impedance is lower, but does not drop so low as to invalidate the 8 Ohm rating.

What is more significant is what it does to the electrical phase. Keep in mind that dropping below the line seen in the graph below indicates capacitive and hence potentially reactive load:

Click the image to open in full size.

We can see the Blue Mark 4 is quite a lot flatter and hence more resistive. But look at 80 Hertz, the negative phase angle in halved, now that is a good thing.

Now let us explore what happens when the Elsinores are driven from a higher impedance amplifier. The below examples simulates 5 Ohm output impedance which is what the JLTi EL34 amp approximates. Most Single-Ended amps, of the tube variety, will also behave similarly, they are all Unity Coupling amps as the output impedance is similar or near that of the speaker's Z.

Below: Red represents a "voltage" amp - one with an impedance well below 1 Ohm, theoretically 0 Ohm. The Blue represents 5 Ohm source Z.

First for Mark 3:

Click the image to open in full size.

Look at round 80-100 Hertz, see how the lines close up. There is certainly more output with Blue (5R) than Red (0R). It will certainly sound richer, but also reacting to other things revealed above.

Now let at look at Mark 4 and how it has improved:

Click the image to open in full size.

Now the addition 5R representing the Unity Coupling amp has very little difference between the two responses. You have to look hard to see there is much a difference.

We would need to see that this also corresponds by comparing the Z plots:

Click the image to open in full size.

Again the shape is well retained.

Final conclusions:

The improvements clearly audible go well beyond that of frequency responses. To describe as damping is too simple. I am not saying that damping is not a factor here, just that there is a lot other things going on. The load conditions imposed on the amplifier and how it copes, also the linearity of the amplifier under dynamic conditions. We now understand that we are much more sensitive to dynamic shadings under a few hundred Hertz than we are the rest of the audio range. We may be less sensitive (but only relatively less) to distortion than compared to critical 2KHz. But the ear/brain uses AGC action to compress dynamics centered around 2KHz but at lower frequencies it is dynamics we sense more acutely. If there is any lag, or any excess energy (damaging downwards dynamics), and these can be caused by so many things (did anybody say power amplifer power supplies?). It comes down to the amp's linear response to dynamics and it's ability to deal with load conditions imposed on it.

The Elsinore simply becomes more amplifer friendly - and it seems both the Elsinores and the amplifier repays in kind. It is just the bass clarity that is improved, but there is also a remarkable improvement in the way the midrange is projected. But again this will depend on what amplifier marriage you have.

Cheers.

Joe R.
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Old 30th April 2010, 08:20 AM   #606
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Quote:
Originally Posted by otto88 View Post
In the PDFs of Scan-Speakís D2608 Discovery tweeter and the Peerless HDS 810921, there are differences.

While the 810921ís PDF was stamped Preliminary, and has a lot less specs, the Sensitivity may not be as high - though the 810921 didnít say if it was @ 2.83 V/ 1m.

More importantly, the response at 30 and 60 degrees apparently now drops off faster . .


Actually the differences do not concern me too greatly. The Z plot looks identical, the characteristic 6-7KHz droop is both there and so is the 14KHz, the high-pass slope (and shape) is not that dissimilar.

I took the graphic of one and expanded it vertically in a paint program to match the visual aspect ratio of the other and it then started to look much closer. The biggest difference is that the raggedness of the 60 degree off axis on D2608 - wouldn't loose to much sleep over that (they could have used a little more smoothing) - I never measure that far off anyway.

They may have revised the dBSPL @ 1M rather than the tweeter. This measurements is always difficult to get right. Even complete speaker systems are difficult to measure and specify the voltage sensitivity.

Speaker measurements change, that doesn't mean the tweeter has changed, not other than batch differences.

If you think the sensitivity has dropped, then slightly lower R3. BTW, this is an 8 Ohm tweeter - to get where it is, it is still drawing half the current and hence have the power, considering that most tweeters are 4 Ohm (some are even 3 Ohm if you ask me). So you get +3dB for free.

Cheers.

Joe
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Old 1st May 2010, 11:38 AM   #607
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Hi Guys

In about a week I will be able to supply really decent set of 6 Dale Vishay 33 Ohm resistors that are required to update from Mark 3 to Mark 4. These are of the type I use my my Elsinores and also crossovers I have built for others.

The cost including shipping will be $30 AUD. PayPal will be OK.

Contact me first and don't send any $ until I confirm stock. I should have enough to supply six sets on a first come first serve basis.

Cheers.

Joe R.
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Old 1st May 2010, 11:55 AM   #608
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Hi Guys

It should also work equally well if you have Mark 1 or 2.

Cheers, Joe
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Old 8th May 2010, 12:33 AM   #609
gabdx is offline gabdx  Canada
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Hi Dr. Rasmussen and others,

I am very interested in building those speakers because of good design, cost quality ratio. I have just a small question on my mind, I would like to know how they sound in comparison to harbeth ?
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Old 8th May 2010, 02:01 AM   #610
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Hi Dr. ?????????????

Never been called that. The best I'd be able to be called is an honourable Doctor.

Anybody seen any spare Doctorates lying around?

You don't mention which Harbeth? But if you are talking about the Harbeth sound, then I would say that you would like the Elsinores. What more can I say.

Cheers.

Joe R.
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